(1) Field of the Invention
This invention relates to masks and methods used for alignment mark recovery after chemical mechanical polishing of an inter-level dielectric, and more particularly to masks and methods for using the masks which do not require additional reticles.
(2) Description of the Related Art
U.S. Pat. No. 5,456,756 to Ramaswami et al. describes a method of protecting alignment marks by using a metal cover over the marks to prevent metal from depositing over the marks on planarized wafers.
U.S. Pat. No. 5,503,962 to Caldwell describes a method of forming additional alignment marks by forming an opening in a planarized inter-level dielectric layer. A conductive material comprising tungsten, having a thickness less than the inter-level dielectric layer, is then deposited in the opening. Chemical Mechanical Polishing is then used to remove the conducting material other than the conducting material in the opening, thereby forming a new alignment mark.
The present invention describes a mask and method for forming a mask protection pattern and a clearout window to recover alignment marks. The mask of this invention is formed from mask elements located in the peripheral region of reticles used to pattern the device regions of a wafer and does not require separate reticles.